The present invention relates generally to synchronization of clocks and, more particularly, to synchronization of clocks in a communication network including packets communicated using a synchronous protocol.
It may be advantageous for devices in a networked system to have a common time base. The common time base may be used, for example, to trigger coordinated measurement instances in a network of sensors or to coordinate actions of controllers in an industrial system. In addition to sensors and controllers, the system may include computers and communication devices, such as routers.
The electronics industry has developed several standard protocols for use in synchronizing clocks, for example, the Precision Time Protocol (PTP) of IEEE 1588. PTP includes sending timing-related messages between nodes in a communication network. The timing-related messages include, for example, a node transmitting a time-stamped packet to supply its time base to another node and a node transmitting a packet requesting the receiving node to reply with the time of receipt. A device that forwards timing-related messages from one node to another node may adjust a timestamp in the messages based on the device's delay in forwarding the message. Any errors or inaccuracies in handling the timing-related messages may be detrimental to accurate clock synchronization and the detriment may be cumulative over multiple network devices.